The numbered versions of Gran Turismo were never about 'professional race cars', they were about the 'street scene'.
Look at Japanese car culture, ordinary-ish production cars tuned, customised and wrapped (normally anime girls).
Yes, GT had high end race cars but it had far more normal cars, even compact Kei cars.
Also Gran Turismo was the only racing game with normal production cars and proper tuning. Not to tell people where to race but if you want BoP then there is GTSport, ACC, all the F1 games..... There should be more races for tuned cars in GT7 and there should be some BoP races for the crowd who just want to pick a car and race.
For me and I guess a large percentage of those who played previous Gran Turismo games, tuning a production car to be competitive is where the enjoyment is; take a normal production car and tune it to eat lambos for breakfast.... Selecting a race and then choosing one of maybe 4 cars and clicking race is so boring, for me.
Real world example: my profile picture is of me welding up a rear pillar on my '91 Range Rover, this has stage 3 heads, torque cam, re-mapped fuel system and de-restricted intake system. It does 0-60mph in less than 5 seconds!
Tuning your car to match how you drive is fun! Try it!😜